Width controlling apparatus and method for rolled strips

ABSTRACT

In a hot tandem rolling mill having a plurality of rolling mill stands, means for controllably applying tension to a strip of material being rolled is provided between said rolling mill stands, thereby to control the width of the rolled strip.

United States Patent Shida et al.

WIDTH CONTROLLING APPARATUS AND METHOD FOR ROLLED STRIPS Shigeru Shida, Hitachi; Sukebumi Tsumura, Mito, both of Japan Inventors:

Foreign Application Priority Data IIII 3,841,124

[ Oct. 15, 1974 [56] References Cited UNITED STATES PATENTS 2,332,803 l0/l943 Lorig 72/205 2,345,765 4/1944 Michel....l 72/205 2,949,799 8/l960 72/234 X 3,220,232 ll/l965 72/7 3,387,472 6/1968 72/17 3.507,l34 SilVI 72/8 PrimaryExaminer-Milton S. Mehr Attorney, Agent, or Firm-Craig & Antonelli get. 1:, japan I 57 ABSTRACT l ln a hot tandem rolling mill having a plurality of rolling mill stands, means for controllably applying ten- CCll. 7243 Sion to a strip of material being rolled is provided Fie'ld "T 17 tween said rolling mill stands, thereby to control the 72/10 ,205, width of the rolled strip 17 Claims, 16 Drawing Figures [A] (BI (01 [D] [E] 1 PA I I38 1 I c 1 I 30 I 13E DEPRESSION DEFRESSION DEPRESSION DEPRESSION DEPRESSION CONTROLLING CONTROLUNG OONTROLUNG CONTROLLING CONTROLLING DEvIcE DEVICE DEVICE DEvIcE DEvIcE Pmmannm 3.841.124

SHEEI 1 0f 8 FIG. I FIG. 2

3 3 |OOOCI TENSION (kg/mm TENSION (kg/mm Low- CARBON STEEL HIGH- CARBON STEEL FIG. 3 FIG. 4

0 IO 20 0 IO 20 TENSION (kg mm TENSION (kg/m'n I8Cr STAINLESS STEEL l8Cr8Ni STAINLESS STEEL PAIENIEuum 1 51914 SHEET 2 OF 8 FIG. 5

FIG. 6-

COMPARATOR OR CALCULATOR slow -Ii ROLLING TEN CONT DEVICE PAImm-uc'z 151524 SHEET 5 OF 8 mob: 30 20 PAIENIEDBBTISIBN 3.841.124

WEN 5 BF 8 I [A] [B] 4 SL :2

TENSION CALCLLATOR CONTR NG \JO DEV'C TYPE OF STEEL STRIP THICKNESS TEMPERATURE VALUES O 0.b.C

PAIEIIIEIIIII a-'.a41'.124

SHEET 7 0F 8 Fl 6. l4

l BA 1, I38 DEPRESSION J DEPRESSION J CONTROLLING CONTROLLING DEVICE DEVICE If 9 Q 65 \7 as i ;|2A {I28 SPEED SPEED OONTROLLINGI CONTROLLING DEVICE DEVICE CALCULATOR f TYPE OF STEEL STRIP THICKNESS TEMPggATURE VALUES OF a,b,c

FIG.

- and apparatus for rolled strips. f

WIDTH CONTROLLING APPARATUS AND METHOD FOR ROLLED STRIPS This invention relates to a. width controlling method of the rolled sheet and removing the edge cracks formed in said rolled sheet in the hot-rolling operation and thereby preventing the growth of cracks or severance of the rolled strip, otherwise occurring in a coldrolling step.

Recently, however, a method has been employed with a view to increasing the available percentage of a rolled material, in which a rolled strip whose edges have not been removed, that is, the so-called nontrimmed strip, is processed through a cold rolling step as it is. In this method, however, since no means has been available heretofore for effectively controlling the width of the rolled strip, the width of the non-trimmed strip has been variable within the range of about mm, with the result that many troubles have been encountered in the subsequent steps of the rolling operation. For instance, since side guides must be set at' an interval slightly larger than the desired width of a rolled strip, the rolled strip tends to make ya zigzag motion during its travel, which not only is detrimental to the strip shape detecting operation but also renders the width control under varying rolling pressure inaccurate. Thus, the conventional method has involved a number of disadvantages from the standpoint of automatic control of the rolling operation.

The present invention contemplates the elimination of such disadvantages as above described, and the purport thereof is to effect the width control of a rolled strip in a hot tandem rolling mill, by controlling the inter-stand tension of the rolling strip.

An object of the present invention is to provide novel control means capable of varying the width of a rolled strip.

Another object of the invention is to control the width of a rolled strip with easiness by simple means based on a new knowledge.-

Still another object of the invention is to providea construction and arrangement, adapted for the control of the width of a rolled strip.

Still another object of the invention is to control the Q width of a rolled strip withv accuracy. v

A further object of the invention is to control the width of a rolled strip predictiveiy. A still further object of the invention is to make it possible to control the width of a rolling strip with. an adequate width changing ratio. An additional object of. the invention is tom e it possible to control the thickness of a rolledstrip, concurrently with-controlling the width thereof.

FIGS. l through 4 are diagrams graphically showing the relationship between the inter-stand tension and the width change, of various rolled steel strips respectively;

FIGS. 5 and 6 are schematic diagrams for explaining the basic concept of the present invention;

FIGS. 7 through 9 are schematic diagrams respectively showing different embodiments of the width control apparatus according to-the invention;

FIG. 10 is an illustrative diagram exemplifying a rolling strip width correcting method;

FIGS. 11 and 12 are schematic diagrams for explainand FIGS. 13 through 16 are schematic diagrams respectively showing different embodiments of the invention.

In the past, no attempthas ever been made, in a hot rolling mill, to positively change the interstand tension of a rolled strip for controlling the width of said rolled strip, but it has been rather the common knowledge in the art, to control the thickness of a rolled strip while conversely maintaining the inter-stand tension of the strip' substantially constant. This is because a thickness variation of the rolling strip incident to tension change is takeninto consideration. v

The present inventors, through strenuous study and experiment, have found a novel rolling strip width con- I trolling method and apparatus in which control means novel over the conventional concept described above or, more specifically, the inter-stand tension of a rolled strip, is positivelyutilized, and which thereby makes it possible tocontrol the width of the rolled strip. The present inventors have made explicit the relationship between the tension and the width change, of various rolled steel strips,'and found that the width of a rolled strip of each steel material can be easily changed by varying the tension in said rolled strip. The present invention has been originated from such knowledge. Namely, such-knowledge has provided a very important basis for the present'inventors to arrive at the present invention.

' FIGS. lthrough 4'exemplify the results of the abovementioned experiment conducted by the present inventors. Namely, FIG. 1 shows the relationship between the tension and the-width change of arolled strip of low-carbon steel; FIG. 2 of high-carbon steel; FIG. 3 of l8-chromium stainless steel and FIG. 4 of l8- chromium -8-nickel stainless steel. As may be understood from these Figures, a width change on the order of 0.5 1.5 percent'or, in other words, a width change of about 10 mm of a rolled strip having a width, for example, of l m, can be obtained very easily by means of a'relatively small tension to the rolled strip. These Fig! ures also show that the desired width control can be sufiiciently achieved by the tension control, at not necessarily all the stands but at only one stand of this type of rolling mill. In this case, it is preferable that the interstand tension control is effected at-the forward stand in response to a command-from tension detector means or plate width detector means. The inter-stand tension is controlled by the forming rollwhose rotatingspeed can, be varied'or by a tensioning roll provided additionally.

Further, it is} best to provide known looper means between the rearward stands for maintaining the strip tension substantially constant.

Another important thing which has been found by they present inventors is how the thickness-of a rolling ing the other basic concept of the present invention;

3 such degree of thickness change is within the tolerance in this type of rolling mill and need not be subjected to control. Even if such a small thickness change is corrected at a subsequent mill stand as being detrimental, a thickness change by such correction is almost negligible. In other words, while the thickness corrective control and width corrective control are correlative theoretically, the amounts of correction are extremely small and practially, can be considered independent of each other. On some occasions, the width control means may be provided in a control system in combination with thickness control means.

Further, since the curve representing the relationship between the tension and the width is relatively steep as seen in FIGS. 1 through 4, it is preferable to control the width, not by detecting the tension but by detecting the width itself, and thereby controlling the rotational speed of the forming rolls or engaging the tensioning roll with the rolled strip, as described above, to chang the inter-stand tension of said rolled strip. 1

In controlling the width by controlling the inter-stan tension of the rolled strip, itis preferable to effect such tension control at the forward stand wherever the circumstances allow and to correct the thickness change, resulting from the tension variation, at the rearward stand, and further, it is best to control said inter-stand tension predictively in response to a command from width detector means provided on the entrance side of the stand. This is because, if the inter-stand tension is controlled in a feedback fashion by a command from width detector means provided on the exit side of the stand, accurate width control will be impossible due to a response delay. For such a predictive control, the factors of the rolled strip, such as the width, the thickness,

the type of steel and the temperature, are previously fed into a calculator or a calculation circuit including a function generator, a multiplienan adder, etc., and a necessary tension corresponding to a deviation of the width from the desired width is determined on the entrance side of the stand, to control predictively the-inter-standtension. In this case, it is necessary to previously store inthe calculator'or the like the relationship between the width deviation and the tension, determined beforehand in the way shown in FIGS. 1 through 4, or contants a, b and c as determined from an established relation represented bynthe following equation, which equation corresponds to equation 13 found'on page 82 of the Aug. 1972 issue of Steel Engineer. 7

T=a(AB/B +b B-H wherein T: the rolling strip tension AB. the'rolling strip width deviation B: the rolling strip width H; the rolling strip thickness a, b, c: constants determined from strip width, strip thickness,'type of steel and temperature It is preferable that the inter-stand tension be controlled by changing the rotational speed ofthe forming rolls or by means of a tensioning roll provided separately, and to provide known looper means between the rearward stands for maintaining the tension substantially constant.

The basic concept of the present invention will be described with reference to FIGS. 5 and 6 which are sche matic views of a hot tandem rolling mill having 5 stands (A) to (E). The rolling mill shown in FIG. 5 comprises a tensioning roll 1 provided between the first two stands for contact with a rolled strip 2, loopers 3 of a known type respectively provided between the other adjacent stands for maintaining the strip tension substantially constant, a width detector 4 provided on the exit side of the last stand (E), a coiler 5 and a guide roll 6. v

In the mill stand shown in FIG. 6, atension'gauge 7 is provided in lieu of and in the same position as the tensioning roll 1 in FIG. 5 and the other construction is the same as that of the rolling mill shown in FIG. 5. In this case, the inter-stand tension of the rolled strip is controlled by varying the rotational speed of the forming rolls.

Although the tensioning roll 1 and the tension gauge 7 are provided only between the first two stands, it should be understood that they may also be provided between the other adjacent stands. It should also be understood that the position of the width detector is not restricted only to the exit side of the last stand.

FIG. 7 shows a practical embodiment of the width controlling apparatus of the invention, which is so designed that the actual width of a rolled strip detected by the width detector 4 is. compared with a predetermined desired width in a comparator or calculator 10, and a tension controlling device 11 is actuated by a signal from said comparator or calculator representative of the width deviation, to operate the tensioning roll 1 to control the inter-stand tension of the rolled strip.

FIG. 8 shows an embodiment in which not only is the width controlled by means of the interstand tension but also a change of the thickness resulting from the tension change is corrected by speed controlling devices 12A, 12B and depression controlling devices 13A, 13B which are operated in response to the signals from the width detector 4 and the comparator or calculator l0.

FIG. 9 shows another embodiment which is of the same construction as that of FIG. 8, except that the tensioning roll 1 in FIG. 8 is replaced by the tension gauge FIGS. 11 and 12 show still other embodiments in which the width detector 4 is provided on the entrance side of the stand (A) of a hot tandem rolling mill having five stands (A) to (E). In FIG.11 reference numeral 1 designates a tensioning roll provided between the first two stands for-contact-with a rolled-strip 2; 3 loopers of a known type provided between the other stands for maintaining the strip tension substantially constant; 5 a coiler and 6 a guide roll. The sameparts as those in sition, the other construction being the same as that of FIG. 11. In this case, the inter-stand tension of the rolled strip is controlled by varying the rotational speed of the forming rolls.

Although the tensioning roll 1 and the tension gauge 7 are provided only between i the first two stands, it should be understood that they may also be provided between the other stands. It should also'be understood that the position of the width detector is not restricted only to the entrance side of the stand A.

FIG. 13 shows a practical embodiment of the width controlling apparatus of the invention, which is so designed that the width of the rolled strip detected by the width detector 4 and a deviation of said detected width from the desired width are fed to the calculator 10 together with the width, the thickness, the type of steel and the temperature, or the values of constants a, b and c, mentioned previously and said calculator l0 emits a signal representative of the value of a necessary tension provided in the same position, and further, not only is the width controlled by means of the interstand tension but also a thickness change caused by the tension change is corrected by the speed controlling devices 12A, 12B .and depression controlling devices 13A, 13B which are operated by a signal from the calculator 10. y

FIG. 15 shows an embodiment in which an additional width detector 4 is provided in another inter-stand space so as to ensure that the relation between the width deviation and the tension is adequate.

FIG. 16 shows by way of example a control system for correcting-the result of width correction in the event when said result of width correction is incorrect, in which the-necessary tensionv is determined from the equation 'givenpreviously, based on the deviation of the width detectedby the width detector 4 from the desired width and the constants-a, b and c as determined from the width, the thickness, the type of steel and the temperature, to control the inter stand tension of a rolled strip and the width of the rolled strip is again detected by. a width detector 4' for comparison with the desired width to correct the constants a, b and c, if necessary. v

What is claimed is:

means for applying tension to a hot rolled strip'passing between the forward rolling mill stands, looper means for maintaining the tension of the rolled strip substantially constant which is passing between the rearward rolling mill stands after its width has been controlled by said tensioning means, means for measuring the width of the rolled strip, first means for generating a. signal representative of a predetermined strip width, second means for generating a deviation signal upon compar; ing a signal from said measuring means with'the signal from said firstmeans, and means for adding said deviation signal to saidtensioning means as a compensation 3 signal.-

2. A width controlling apparatus for rolled strips, for use in a hot tandem rolling mill, comprising tensioning means for applying tension to a hot rolled strip passing between the rolling mill stands, means for measuring the width of the rolled strip, first means-for generating a signal representative of a predetermined strip width, second means for generating a deviation signal upon comparingva signal from said stripwidth measuring means with the signal from said firstmeans, means for simulating the desired tension to be applied to the rolled strip from various factorsof said rolled strip andmeans being disposed downstream of said tensioning means; means for calculating a desired tension value by utilizing measurements of the strip width as an input,

and tension control means for sending an output to said tensioning means by utilizing the desired tension value as an input. v

4. A strip width controlling apparatus for rolled strip in a hot tandem rolling mill, the control apparatus comprising: tensioning means for applying tension to a hot rolled strip passing between rolling mill stands of the hot tandem rolling mill; means for measuring the tension, means for measuring the width of the rolled strip;

means for simulating a desired tension and a desired depression ratioby utilizing tension measurements and strip width measurements as an input; means for controlling roll speed of said rolled stripby utilizing the simulated tension and depression ratio as an input signal; and means for controlling the roll depression by utilizing the simulated signals of the tension and depression ratio as an input signal. 7

5. A width controlling apparatus according to claim 4, wherein the hot tandem rolling mill includes a pair l. A width controlling apparatus for rolled strips, for .use in a hot tandem rolling mill, comprising tensioning of rolling mill stands, and wherein said means for measuring the width of the rolled strips is disposed downstream of the second of said pair of rolling mill stands.

8. A width controlling apparatus according to claim 4, wherein the hot tandem rolling mill has at least three rolling mill stands, and wherein said means for measuring the width of the rolled strip is disposed downstream of the last of said rolling'mill stands, and wherein means are provided between atleast the second and third roll mill stand for maintaining the strip width substantially constant. r

9. A width controlling apparatus accordingto claim 8, wherein said means for applying tension includes a tensioning roller disposed between the first and second rolling mill stands. a

10. A width controlling apparatus according to claim 8, wherein a tension gauge is disposed at least between v the first and second rolling mill stands.

11'. A width controlling arrangement according to claim 4, wherein means are provided downstream of a rolling mill stand for compensating for an insufficient strip width correction in said rolling mill stand.

15. A width controlling apparatus according to claim 13, wherein at least one tensioning gauge is disposed between at least a pair of adjacent rolling mill stands.

16. A width controlling apparatus according to claim 4, wherein a pair of widthmeasuring means are provided.

17. A width controlling arrangement according to claim 16, wherein at least one of said pair of width measuring means is disposed upstream of a first rolling mill stand. 

1. A width controlling apparatus for rolled strips, for use in a hot tandem rolling mill, comprising tensioning means for applying tension to a hot rolled strip passing between the forward rolling mill stands, looper means for maintaining the tension of the rolled strip substantially constant which is passing between the rearward rolling mill stands after its width has been controlled by said tensioning means, means for measuring the width of the rolled strip, first means for generating a signal representative of a predetermined strip width, second means for generating a deviation signal upon comparing a signal from said measuring means with the signal from said first means, and means for adding said deviation signal to said tensioning means as a compensation signal.
 2. A width controlling apparatus for rolled strips, for use in a hot tandem rolling mill, comprising tensioning means for applying tension to a hot rolled strip passing between the rolling mill stands, means for measuring the width of the rolled strip, first means for generating a signal representative of a predetermined strip width, second means for generating a deviation signal upon comparing a signal from said strip width measuring means with the signal from said first means, means for simulating the desired tension to be applied to the rolled strip from various factors of said rolled strip and said deviation signal, and means for applying a signal from said simulating means to said tensioning means.
 3. A strip width controlling apparatus for rolled strips in a hot tandem rolling mill having a plurality of mill stands, the control apparatus comprising: means disposed between at least a pair of adjacent mill stands for applying tension to a hot rolled strip passing therebetween; means for maintaining the tension of the rolled strips substantially constant after its strip width has been controlled by said tensioning means; means for measuring the width of the rolled strip, said measuring means being disposed downstream of said tensioning means; means for calculating a desired tension value by utilizing measurements of the strip width as an input, and tension control means for sending an output to said tensioning means by utilizing the desired tension value as an input.
 4. A strip width controlling apparatus for rolled strip in a hot tandem rolling mill, the control apparatus comprising: tensioning means for applying tension to a hot rolled strip passing between rolling mill stands of the hot tandem rolling mill; means for measuring the tension, means for measuring the width of the rolled strip; means for simulating a desired tension and a desired depression ratio by utilizing tension measurements and strip width measurements as an input; means for controlling roll speed of said rolled strip by utilizing the simulated tension and depression ratio as an input signal; and means for controlling the roll depression by utilizing the simulated signals of the tension and depression ratio as an input signal.
 5. A width controlling apparatus according to claim 4, wherein the hot tandem rolling mill includes a pair of rolling mill stands, and wherein said means for measuring the width of the rolled strips is disposed downstream of the second of said pair of rolling mill stands.
 6. A wiDth controlling apparatus according to claim 5, wherein said means for applying tension includes a tensioning roll disposed between said pair of rolling mill stands.
 7. A width controlling apparatus according to claim 5, wherein a tensioning gauge is disposed between said pair of rolling mill stands.
 8. A width controlling apparatus according to claim 4, wherein the hot tandem rolling mill has at least three rolling mill stands, and wherein said means for measuring the width of the rolled strip is disposed downstream of the last of said rolling mill stands, and wherein means are provided between at least the second and third roll mill stand for maintaining the strip width substantially constant.
 9. A width controlling apparatus according to claim 8, wherein said means for applying tension includes a tensioning roller disposed between the first and second rolling mill stands.
 10. A width controlling apparatus according to claim 8, wherein a tension gauge is disposed at least between the first and second rolling mill stands.
 11. A width controlling arrangement according to claim 4, wherein means are provided downstream of a rolling mill stand for compensating for an insufficient strip width correction in said rolling mill stand.
 12. A width controlling arrangement according to claim 11, wherein said compensating means includes at least one tensioning roller disposed between adjacent rolling mill stands.
 13. A width controlling apparatus according to claim 4, wherein said means for measuring the width of the rolled strip is disposed upstream of a first rolling mill stand.
 14. A width controlling apparatus according to claim 13, wherein said means for applying tension includes at least one tensioning roller disposed between at least a pair of adjacent rolling mill stands.
 15. A width controlling apparatus according to claim 13, wherein at least one tensioning gauge is disposed between at least a pair of adjacent rolling mill stands.
 16. A width controlling apparatus according to claim 4, wherein a pair of width measuring means are provided.
 17. A width controlling arrangement according to claim 16, wherein at least one of said pair of width measuring means is disposed upstream of a first rolling mill stand. 